The
2010 Alexandrium forecast for the Gulf of Maine was not borne out
by cruise observations and shellfish toxicity measurements. We
predicted a large regional bloom in the WGOM that did not happen.
Toxicity along the coast has been low, and cruise data show very few
cells in the region from Massachusetts and Cape Cod Bays to mid-coast
Maine.

Two possible (and potentially related ) reasons for the absence of
the bloom in the WGOM are evident thus far: 1) there was a water
mass change that lies outside the envelope of observations from at
least the last six years, which were the basis of the ensemble
forecast that led to the 2010 prediction; and 2) along-coast surface
transport off southern Maine was slower than normal.

The deep basins of the Gulf of Maine were warmer than was observed in
2003 - 2008. This water mass anomaly affects intermediate and
surface waters where Alexandrium resides. In fact, surface waters
were several degrees warmer than in 2008, when a large Alexandrium
bloom took place. Stratification, nutrient concentrations,
grazers,
and other factors critical to Alexandrium growth could all have been
affected. Our GOMTOX cruise data are being used to assess these
factors.

Should we be able to deduce the mechanisms responsible for the lack
of a bloom in the WGOM in 2010, those processes could then be
included in the population dynamics model. Furthermore, we note
that
the water mass changes mentioned above relate to the larger scale
circulation of the northwest Atlantic, and therefore are observable
months in advance of the Alexandrium season. Therefore, it is
conceivable that forecasts can be made taking into account this type
of variability. It is indeed fortunate that GOMTOX cruises were
scheduled for 2010, as this will allow us to understand the factors
that prevented a bloom and thereby allow us to improve our model.